1. Field
The following description relates to signal processing technology and amplification processing technology, and more particularly, to technology for controlling an output distortion that may arise due to a change in supply voltage.
2. Description of the Related Art
A digital amplifier functions to modulate and amplify input signals. In an output terminal of a digital amplifier, active elements such as transistors may be formed in a bridge structure. In operating the digital amplifier, it may be desirable to have constant external power supplied to the output terminal.
If a supply voltage to be applied to the output terminal is cut off intermittently or fluctuates, an output signal of the digital amplifier may be distorted. In the case of a digital amplifier which processes audio signals, such fluctuations in supply voltage may cause the sound-quality deterioration.
In attempt to address the above, two approaches have been considered.
A first approach is to adopt a power supply with a sufficient capacity. However, this method is believed to face limitations in terms of manufacturing costs. The expense of constantly maintaining enough voltage can be expensive, and unnecessary. The other approach is to compensate for supply voltage fluctuations by controlling changes in characteristics caused by the supply voltage fluctuations. A representative example is a feedback control scheme that controls the differences between output signals and ideal signals. However, since such a feedback control scheme uses error signals generated in the previous step, there are difficulties in real-time control. Furthermore, there is no solution for supply voltage fluctuations that occur in transitional periods such as at the start and the end of a control operation.